There’s a new kind of algorithm that allows you to take a video of one person and map the face of another person onto his or her body. Not surprisingly, it’s being used to map celebrities’ faces onto the bodies of porn stars having sex. Vox’s Aja Romano tells Sean Rameswaram how “deepfakes” are spreading across the internet. Plus computer scientist Peter Eckersley explores how the same technology could tear our society apart in bigger ways.